Why did the chimp cross the road?

Chimp or lollipop man? Dominant chimps look both ways to see if the road's clear before shepherding other chimps across (Image: iStockphoto)

Adult male chimpanzees act like school lollipop men by leading smaller chimps across roads that dissect their forest habitats, according to a new study.

The finding demonstrates that chimps display concern for family and friends and will risk their own safety to ensure the welfare of others.

Scientists now believe such ability for care and consideration is present in certain primates, and not just humans.

"I think that we would definitely see this kind of behaviour in other great ape species, and different populations may reveal cultural differences in protective orderings," says Kimberley Hockings, lead author of the study, which is published in the journal Current Biology.

Hockings, a researcher at the University of Stirling in Scotland, and colleagues observed a group of wild chimps in Bossou, Guinea, West Africa.

The chimp group consisted of three adult males, five adult females, three juveniles and one infant.

Two roads dissect the chimps' forest homeland. The first is a narrow road used by pedestrians, while the second is wider and carries trucks, motorbikes, cars, as well as pedestrians.

The scientists analysed 19 instances where the chimpanzees crossed the two roads.

In each instance, an adult male, often the alpha male named Yolo, would stand at the edge of the road. He then would carefully look left and right, then motion with an arm.

At that point, the other chimps formed themselves into an ordered line and followed behind. The order nearly always consisted of adult males first with females, juveniles and the infant second. The leader, or another adult male, would then wait at the end of the line to assist the littlest ones.

When crossing the heavier traffic road, the second ranked male, Foaf, would continue to scan for vehicles and people while the elderly third male, Tua, and the alpha female took the lead.

The researchers noted that the female would move into the more forward, leader position when the degree of crossing risk increased.

"They tend to travel in such ordered lines in risky situations such as road crossing and crop raiding," says Hockings.

"Depending on the situation, when moving through the forest, it is much more common that the chimpanzees are spread out."

Dr Klaus Zuberbühler is a University of St Andrews scientist who conducts research on the cognitive capacities of non-human primates. The Scotland-based scientist calls the findings "amazing".

"What's perhaps most striking is that Kimberly's research shows that these free-ranging chimpanzees are not indifferent to the welfare of other group members, in contrast to previous findings reported from captive chimpanzees," Zuberbühler says.

"They appear to have an understanding of other group members' vulnerability and they take action in response to this knowledge.

"It also highlights the importance of studying the cognitive capacities of primates in the wild. The majority of research on chimpanzee intelligence is currently conducted in highly deprived lab situations, and, perhaps unsurprisingly, individuals often show little or no interest in engaging in cooperative or altruistic acts."

Hockings hopes future research will determine similar progression orders in other great ape populations, which could reveal how human social organisation probably emerged in our distant primate ancestors.